Liquid crystal display devices have been applied to, for example, watches, calculators, a variety of measuring equipment, panels used in automobiles, word processors, electronic notebooks, printers, computers, television sets, clocks, and advertising boards. Representative examples of types of liquid crystal display devices include a TN (twisted nematic) type, an STN (super twisted nematic) type, and vertical alignment and IPS (in-plane switching) types involving use of a TFT (thin film transistor). Liquid crystal compositions used in such liquid crystal display devices need to satisfy the following requirements: being stable to external stimuli such as moisture, air, heat, and light; having a liquid crystal phase in a wide temperature range mainly including room temperature as much as possible; having a low viscosity; and enabling a low driving voltage. In addition, liquid crystal compositions are composed of several to tens of compounds in order to adjust, for example, the dielectric anisotropy (Δ∈) and refractive index anisotropy (Δn) to be optimum to individual display devices.
A liquid crystal composition having a negative Δ∈ is used in vertical alignment (VA)-type displays, and a liquid crystal composition having a positive Δ∈ is used in horizontal alignment-type displays such as a TN type, an STN type, and an IPS (in-plane switching) type. Another type of driving has been reported, in which the molecules of a liquid crystal composition having a positive Δ∈ are vertically aligned in a state in which voltage is not applied, and then a horizontal electric field is applied for performing display. A demand for a liquid crystal composition having a positive Δ∈ has therefore further increased. In all types of driving, however, there have been demands for driving at low voltage, a quick response, and a broad range of operating temperature. In other words, a liquid crystal composition having a positive Δ∈ with a large absolute value, a low viscosity (II), and a high nematic phase-isotropic liquid phase transition temperature (Tni) has been demanded. In order to control Δn×d that is a product of Δn and a cell gap (d) to be a predetermined value, the Δn of a liquid crystal composition needs to be adjusted to be in a proper range on the basis of the cell gap. In addition, a quick response is important in liquid crystal display devices applied to television sets or other apparatuses, which generates a need for a liquid crystal composition having a small rotational viscosity (γ1).
Liquid crystal compositions which enable a quick response have been disclosed; for example, such liquid crystal compositions contain a combination of liquid crystal compounds having a positive Δ∈ and represented by Formulae (A-1) and (A-2) and a liquid crystal compound having a neutral Δ∈ and represented by Formula (B). In these liquid crystal compositions, the liquid crystal compound having a positive Δ∈ has a —CF2O— moiety, and the liquid crystal compound having a neutral Δ∈ has an alkenyl group; it is widely known in the field of liquid crystal compositions (see Patent Literatures 1 to 4).

As liquid crystal display devices have come to be used in a broad range of applications, usage and manufacturing thereof have been greatly changed. In order to adapt to such changes, optimization of characteristics other than known basic physical properties has been needed. In particular, a VA type and an IPS type have become popular as liquid crystal display devices utilizing a liquid crystal composition, and these types of display devices having a very large size (e.g., 50 inches or lager) have also been practically used. An increase in the size of substrates has changed a technique for putting a liquid crystal composition between the substrates, and a one-drop-fill (ODF) technique has become mainstream in place of a typically employed vacuum injection technique. Dropping of a liquid crystal composition onto a substrate, however, generates droplet stains with the result that display quality is degraded, which has been problematic.
Furthermore, in a process for manufacturing a liquid crystal display device by an ODF technique, a liquid crystal material needs to be dropped in an amount optimum for the size of the liquid crystal display device. In the case where the amount of a liquid crystal material to be dropped largely varies from the optimum level, a predetermined balance between a refractive index and a driving electric field in a liquid crystal display device is disrupted, which causes defective display such as unevenness and defective contrast. In particular, the optimum amount of a liquid crystal material to be dropped is small in small-size liquid crystal display devices well used in smartphones which have become popular in recent years, and thus it is difficult even to control a variation from the optimum amount to be in a certain range. Hence, in order to maintain a high yield of liquid crystal display devices, for instance, a liquid crystal composition needs to be less affected by a rapid pressure change and impact generated on dropping of the liquid crystal composition in a dropping apparatus and to be able to be stably and continuously dropped for a long time.
In terms of these circumstances, a liquid crystal composition which is used in active-matrix liquid crystal display devices driven by, for example, TFT devices needs to be developed for satisfying requirements for liquid crystal display devices, such as enabling quick response and having a high specific resistance, a high voltage holding ratio, and improved stability to external elements such as light and heat, also in view of a manufacturing process of liquid crystal display devices.